Rules for magnetic ballasts?

[onewarmguy]

Hey folks, I got an amazing deal on a used 1000W HPS system, 48" reflector, MH/HPS magnetic ballast and 2 HPS bulbs. I'm thinking that 1000W is a little much for 2 plants, which is all I ever have growing, can I use a 400 or 600 bulb with the 1000W ballast? Or is that a no no?

Also how much heat are we talking about here, I have a 4' diameter grow enclosure with an open top, is my garage going to cook?

Thanks
Onewarmguy

 

[onewarmguy]

btt